JP2002097459A - Abrasive agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-performance abrasive agent for an insulation film layer for semiconductors permitting improvement in an abrasion speed and concurrent reduction in scratch and dust on abrading an insulation film layer for semiconductors by the CMP method. SOLUTION: The abrasive agent comprises a slurry comprising an aqueous solution having dispersed therein oxide particles comprising cerium as a constituting atom, where the ζ potential of the oxide particles is -10 mV or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor substrate, a wiring substrate, a semiconductor device, a glass material, a hard disk, a photomask, a glass substrate such as a liquid crystal display, an optical lens, a crystal oscillator, a magnetic head, a video deck head,
The present invention relates to an abrasive preferably used for an optical fiber connector and the like. More specifically, the present invention relates to an abrasive comprising a slurry in which oxide particles having cerium as constituent atoms are dispersed in an aqueous solution.

[0002]

2. Description of the Related Art In recent years, with the increase in the degree of integration of semiconductor devices, the minimum processing line width accompanying the increase in the number of wiring layers and the miniaturization of wiring patterns has been progressing in the direction of adopting fine line widths on the order of 0.1 μm. I am doing it.

Accordingly, in order to compensate for the lack of depth of focus of an exposure apparatus for drawing a wiring pattern, it is necessary to flatten the device surface in an intermediate step of semiconductor device manufacturing.

[0004] As a method of such flattening, an etch-back method, a reflow method, or a chemical mechanical polishing method (abbreviated as CMP method) is used.
g), etc., a technology to polish the interlayer insulating film such as silica so as to have a uniform thickness has been developed. However, since it is particularly effective for global flattening derived from the density of wiring,
The CMP method has become mainstream.

At present, in the CMP method, a technique using a slurry liquid containing silica particles and a slurry liquid containing cerium oxide particles has been industrially put to practical use.

Among them, the slurry liquid containing silica particles has the highest versatility, but the slurry liquid containing silica particles has
In order for the polishing liquid to have an etching action, it is necessary to make the polishing liquid highly alkaline, and there are problems such as an increase in impurities such as potassium and a reduction in polishing rate, depending on the strong alkaline solution used.

On the other hand, the slurry containing cerium oxide particles has a high polishing rate because of its high reactivity with silica as a material of the insulating film. However, scratches called scratches are generated on the surface of the material to be polished. In addition, there is a problem that cerium oxide particles easily remain on the surface to be polished, generating so-called dust.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is, for example, in polishing a semiconductor insulating film layer by a CMP method.
It is an object of the present invention to provide a high-performance semiconductor insulating film layer polishing slurry which can improve the polishing rate and at the same time reduce scratches and dust.

[0009]

Means for Solving the Problems To solve such problems, the abrasive of the present invention has the following constitution. That is, it is an abrasive made of a slurry liquid in which oxide particles having cerium as constituent atoms are dispersed in an aqueous solution, and the zeta potential of the oxide particles is −10 mV or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies and as a result,
An abrasive comprising a slurry liquid in which oxide particles, for example, cerium or oxide particles having cerium and zirconium as constituent atoms (hereinafter simply referred to as oxide particles) are dispersed in an aqueous solution, Surprisingly, it has been found that the above-mentioned problems can be solved at once by using an abrasive having a zeta potential of a specific value or less in an aqueous solution of particles.

The abrasive according to the present invention is preferably used for polishing an insulating film layer in a semiconductor manufacturing process. In particular, it can be preferably applied to a method called STI (Shallow Trench Isolation) for uniformly polishing the surface of an insulating film using a difference in polishing rate between a stop film made of silicon nitride or the like and an insulating film made of silica or the like.

In the present invention, it is necessary that cerium is a constituent atom of the oxide particles used in the abrasive, and it is more preferable that cerium and zirconium are constituent atoms. Specifically, cerium oxide and zirconium oxide react with each other to form a compound, for example, cerium oxide or cerium oxide (hereinafter collectively referred to as cerium oxide) and zirconium oxide form a solid solution. In this case, a simple mixture of these atoms can be used.

The composite oxide particles forming a solid solution can be obtained, for example, by the following method.

A water-soluble trivalent cerium compound such as cerium nitrate, cerium sulfate and cerium chloride is mixed with a water-soluble zirconium compound such as zirconium oxychloride in an aqueous solution, and the mixture is reacted by adding aqueous ammonia or the like. Then, a water-insoluble compound of cerium and zirconium is formed, and an oxidizing agent such as hydrogen peroxide is further added to perform oxidation treatment.

Next, the solution is filtered and centrifuged to collect a coprecipitate composed of composite oxide particles. Here, in order to increase the purity of the composite oxide particles, it is effective to repeatedly wash the coprecipitate with ultrapure water or the like.

Next, after drying the coprecipitate, the coprecipitate is dried in an oven for 3 hours.
By performing a heat treatment at a temperature of 00 ° C. or higher, powder of composite oxide particles is obtained.

The composite oxide particles have an average primary particle size of 10 to 1000 nm, preferably 50 to 50 nm.
It is good to be 0 nm. When it is less than 10 nm, the particles are too fine, and when used as a polishing agent for an insulating film layer of a semiconductor, the polishing performance may be poor.
If it exceeds nm, scratches may occur on the surface to be polished. Here, the “primary particle” refers to a minimum unit of particles constituting a powder or an aggregate that can exist without breaking bonds between molecules.

The average particle diameter of the primary particles can be determined, for example, by observing a TEM photograph obtained by a transmission electron microscope (TEM) in an enlarged manner for each primary particle, and determining an equivalent circle diameter by image processing. Can be determined from the 50% diameter (median diameter) in the particle size distribution.

In the present invention, the content of impurities such as sodium, copper, iron, aluminum and calcium in the oxide particles is less than 1% by weight, preferably 0% by weight, based on 100% by weight of the total oxide particles. It is better to be less than 0.5% by weight. If the content of the impurities is 1% by weight or more, the impurities may remain in the semiconductor to be polished, and may deteriorate the quality of the semiconductor. still,
The content of this impurity can be measured by ICP emission spectroscopy.

The slurry of the present invention, that is, the slurry containing the composite oxide particles, can be obtained by dispersing the composite oxide particles obtained by the above-described method in an aqueous solution as usual. . The distribution method here is
For example, a method using an ordinary stirrer, a method using a ball mill or the like can be adopted.

For dispersion, it is preferable to add a dispersant. As the dispersant, those containing no metal ions can be preferably used. Specifically, water-soluble organic polymers such as ammonium salts of polyacrylic acid and polyvinyl alcohol; water-soluble anionic surfactants such as ammonium lauryl sulfate; and water-soluble nonionic surfactants such as polyethylene glycol monostearate. Activators and water-soluble amines such as monoethanolamine. If the dispersant is not added, particles may adhere to the surface of the material to be polished to form so-called dust, or the dispersibility of the slurry liquid may decrease. In the present invention, the oxide particles have a zeta potential in an aqueous solution of −10 mV or less, preferably −20 mV or less. If it exceeds -10 mV, the dispersibility of the particles is reduced, and scratches and dust may be generated on the surface of the object to be polished.

Incidentally, if the zeta potential is -30 mV, it is often sufficient to achieve the effects of the present invention.

In the present invention, such zeta potential can be measured by laser Doppler electrophoresis. Here, Otsuka Electronics Co., Ltd. is an example of a measuring device.
Using an electrophoretic light scattering photometer (model: ELS-800) and measuring conditions: light source: He-Ne laser, cell: membrane-isolated rectangular cell (2 mm * 10 mm *)
17 mm), measurement mode: heterodyne method, voltage: 80
V, measurement temperature: 25 ° C., measurement angle: 20 °, measurement room atmosphere: 23 ± 2 ° C., 50 ± 5% RH, dispersion medium: distilled water (for ion chromatography, manufactured by Wako Pure Chemical Industries, Ltd.) I do.

In the present invention, an abrasive made of a slurry liquid in which oxide particles are dispersed in an aqueous solution has a pH of 3
-11, preferably 5-9. When the pH is out of the above range, the degree of acidity or alkalinity is increased, which may make it difficult to treat wastewater or corrode a manufacturing apparatus.

[0025]

(Example 1) 2500 g of cerous chloride aqueous solution having a cerium oxide concentration of 24% by weight and zirconium oxide so that the mixing ratio of cerium oxide and zirconium oxide becomes 60:40 in terms of weight. Was mixed with 2,000 g of an aqueous solution of zirconium oxychloride having a concentration of 20% by weight and stirred to prepare a mixed aqueous solution of cerous chloride and zirconium oxychloride.

Next, 3000 g of aqueous ammonia having a concentration of 7% by weight was added to the aqueous solution and stirred to adjust the pH of the aqueous solution to 7%.
And Furthermore, 77 g of hydrogen peroxide solution was added and stirred,
A coprecipitate of cerium hydroxide and zirconium hydroxide was obtained.

The aqueous solution containing the coprecipitate was heated in an autoclave at 150 ° C. for 24 hours, and filtration and washing were repeated several times, and then dried to obtain a composite oxide powder.

This powder was fired at 1050 ° C. for 2 hours to obtain a powder of composite oxide particles. The average particle size of the primary particles of the particles constituting the present powder is 88 nm, and the content of impurities is 0.2
% By weight.

Next, 2700 g of pure water was added to 300 g of the powder of the composite oxide particles, and the mixture was mixed by a ball mill for 24 hours to obtain a slurry containing the composite oxide particles.

Next, the concentration of the composite oxide particles in the slurry liquid was adjusted to 10% by weight, and an ammonium salt of polyacrylic acid as a dispersant was added to 100% by weight of the composite oxide particles contained in the slurry liquid. Add 10% by weight, stir and dilute further with pure water, concentration 1% by weight, pH 7.4
An abrasive comprising a slurry liquid in which the composite oxide particles were dispersed in an aqueous solution was obtained.

The zeta potential of the composite oxide particles in the slurry was -20 mV.

Using this polishing agent, a silicon oxide film (insulating film layer) (size, type: 15 mm ×
(15 mm square) was polished with the following apparatus and conditions.

Polishing device: Lapping machine (Musashino Electronics Co., Ltd., model number: MA-200) Polishing pad: IC1000 / SUBA400 (Rodel Nitta) Load: 200 g / cm ² Platen rotation speed: 60 rpm Work rotation Number: 60 rpm Polishing time: 5 minutes Abrasive supply amount: 24 cc / min Here, the silicon oxide film after polishing was evaluated by the following apparatus and method.

Measurement of film thickness: Film thickness meter (Lambda Ace, manufactured by Dainippon Screen Co., Ltd.) Observation of scratches and dust: Visual observation using a microscope (manufactured by Keyence Corporation).

The polishing rate was determined by dividing the change in film thickness by the polishing time (5 minutes).

From the above, the following results were obtained.

Polishing rate: 136 nm / min. Scratch: not recognized.

Dust: not observed. (Example 2) Example 1 was repeated except that zirconium oxide was not added (cerium oxide alone).
The polishing agent was adjusted in the same manner as described above, and the silicon oxide film was polished on the silicon wafer and evaluated.

Here, the oxide particles had an average primary particle diameter of 148 nm and an impurity content of 0.2% by weight.

Further, the prepared abrasive had a concentration of 1% by weight and a pH of 7.5.

The zeta potential of the oxide particles in the slurry was -26 mV.

From the above, the following results were obtained.

Polishing rate: 92 nm / min. Scratch: not recognized.

Dust: not observed. (Example 3) In the same manner as in Example 1 except that the mixing ratio of cerium oxide and zirconium oxide was 80:20 in terms of weight and the slurry concentration was 1.5% by weight,
The polishing agent was adjusted, and the silicon oxide film was polished on the silicon wafer and evaluated.

Here, the composite oxide particles had an average primary particle size of 90 nm and an impurity content of 0.2% by weight.

Further, the prepared abrasive had a concentration of 1.5% by weight and a pH of 7.1.

The zeta potential of the composite oxide particles in the slurry was -18 mV.

From the above, the following results were obtained.

Polishing rate: 128 nm / min. Scratch: not recognized.

Dust: not observed. (Comparative Example 1) An abrasive was prepared, and a silicon oxide film on a silicon wafer was polished and evaluated in the same manner as in Example 1 except that the pH was adjusted to 2 with hydrochloric acid during slurry preparation.

Here, the composite oxide particles had an average primary particle size of 88 nm and an impurity content of 0.2% by weight.

Further, the prepared abrasive had a concentration of 1% by weight and a pH of 2. The zeta potential of the composite oxide particles in the slurry was +5 mV.

From the above, the following results were obtained. Polishing rate: 200 nm / min Scratch: observed. -Dust: recognized. Comparative Example 2 An abrasive was prepared in the same manner as in Example 1 except that the mixing ratio of cerium oxide and zirconium oxide was 80:20 in terms of weight, and the pH was adjusted to 1.5 with hydrochloric acid during slurry adjustment. Was prepared, and the silicon oxide film on the silicon wafer was polished and evaluated.

Here, the composite oxide particles had an average primary particle size of 90 nm and an impurity content of 0.2% by weight.

Further, the prepared abrasive had a concentration of 1% by weight and a pH of 1.5. The zeta potential of the composite oxide particles in the slurry was +10 mV.

From the above, the following results were obtained. Polishing rate: 190 nm / min Scratch: observed. -Dust: recognized.

[0057]

According to the present invention, a slurry liquid is prepared by dispersing oxide particles, for example, oxide particles having cerium as constituent atoms or composite oxide particles having cerium and zirconium as constituent atoms in an aqueous solution. Since a polishing agent is used in which the zeta potential of the oxide particles is −10 mV or less, for example, in polishing a semiconductor insulating film layer by a CMP method, the polishing speed is markedly improved while simultaneously scratching. And dust can be significantly reduced.

Claims (8)

[Claims] An abrasive comprising a slurry liquid in which oxide particles having cerium as constituent atoms are dispersed in an aqueous solution, wherein the oxide particles have a zeta potential of -10 mV or less. 2. An abrasive according to claim 1, wherein said oxide particles are composite oxide particles containing cerium and zirconium as constituent atoms. 3. The polishing agent according to claim 1, wherein the polishing agent is used for polishing an insulating film layer in a semiconductor manufacturing process. 4. An abrasive according to claim 3, which is used for shallow trench isolation. 5. The oxide particles having an average primary particle size of 1
The abrasive according to any one of claims 1 to 4, which has a thickness of 0 to 1000 nm. 6. The abrasive according to claim 1, wherein the content of impurities contained in said oxide particles is less than 1% by weight based on 100% by weight of all oxide particles. 7. The abrasive according to claim 1, wherein a dispersant is added to said slurry liquid. 8. The polishing agent according to claim 1, which has a pH of 3 to 11.